Rice (Oryza sativa L.) is one of the most important food crops in the world, providing 35-60% of the dietary calories. It is consumed by more than 3 billion people. Rapid population growth and economic development are growing pressures for an increase in food production. To increase yield further and to break the yield ceiling, breeding efforts of scientists all over the world focused on expanding the yield sink capacity (the maximum size of sink organs to be harvested) mainly by increasing the number of spikelets per panicle (Kato et al 2007: Plant Production Science; 10: 442-450). As a result, cultivars with large panicles or extra-heavy panicle types with numerous spikelets per panicle have become available, such as the New Plant Type of the International Rice Research Institute and Super rice of China (Cheng et al., 2007Annals of Botany 100, 959-966). These cultivars do not exhibited their high yield potential due to their poor grain-filling, as in a slow grain-filling rate and many unfilled grains (Ao et al., Scientia Agricultura Sinica 41, 1927-1936 (2008)), and World community was unable to increase potential yield of rice. The present invention is quite different from the approach of the other Rice Scientists of the World Community.